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Abstract:

The present specification relates to an apparatus and method for
transceiving signals between a terminal and a base station in a wireless
communication system. The present specification relates to a
signal-transceiving method in which location reference signals
discriminated by frequency units for each base station, such that base
stations which transmit location reference signals with the same location
reference signal pattern can be further discriminated.

Claims:

1. A method of transmitting a signal in a wireless communication system,
the method comprising the steps of: dividing, into L frequency bands, a
total frequency band allocated to a frequency axis with respect to N
consecutive subframes that are allocated for transmitting a positioning
reference signal (PRS) at regular intervals; and performing muting by not
transmitting a PRS to at least one frequency band with respect to at
least one of the N subframes, and transmitting a PRS to remaining
frequency bands.

2. The method as claimed in claim 1, wherein, when L is 2, the method
comprises the steps of: dividing the total frequency band allocated to
the N subframes into two frequency bands; and repeatedly performing a
frequency muting pattern based on a two-subframe unit, wherein the
frequency muting pattern comprises: performing muting by not transmitting
a PRS to at least one frequency band, and transmitting a PRS to a
remaining frequency band.

3. The method as claimed in claim 2, wherein: one of the two frequency
bands transmits a PRS with respect to the N consecutive subframes
allocated for transmitting a PRS at regular intervals; and the other
frequency band performs muting by not transmitting a PRS with respect to
the N consecutive subframes allocated for transmitting a PRS at regular
intervals.

4. The method as claimed in claim 2, wherein: one of the two frequency
bands transmits a PRS to one subframe in the two-subframe unit, and
performs muting by not transmitting a PRS to the other subframe; the
other frequency band transmits a PRS to the other subframe, and performs
muting by not transmitting a PRS to the one subframe; and the frequency
muting pattern is repeatedly performed with respect to N consecutive
subframes allocated for transmitting a PRS at regular intervals.

5. The method as claimed in claim 1, wherein, when L is 3, the method
comprises the steps of: dividing the total frequency band allocated to
the N subframes into three frequency bands; and transmitting a PRS or
performing muting by not transmitting a PRS, and repeatedly performing a
frequency muting pattern based on a three-subframe unit.

6. The method as claimed in claim 5, wherein, from among three frequency
bands obtained by dividing the total frequency band allocated for the N
consecutive subframes: one frequency band transmits, based on a
three-subframe unit, a PRS at a first subframe of a first frequency band
(F0) from among the N consecutive subframes, and performs muting by not
transmitting a PRS at a second subframe and a third subframe; another
frequency band transmits a PRS at the second subframe, and performs
muting by not transmitting a PRS at the third subframe and the first
subframe; and the other frequency band transmits a PRS at the third
subframe, and performs muting by not transmitting the PRS at the first
subframe and the second subframe.

7. The method as claimed in claim 1, wherein the N subframes are
allocated for transmitting a PRS at regular intervals, N is one of 2, 4,
and 6, and the regular intervals is one of 160 ms, 320 ms, 640 ms, and
1280 ms.

8. The method as claimed in claim 1, wherein a pattern of a PRS of a
subframe forms, based on a predetermined sequence, a basic PRS pattern in
1/2 of a resource block including two slots forming a single subframe and
six OFDM subcarriers, forms a primary basic PRS pattern in a location of
a subcarrier on a frequency domain corresponding to an ith value of
the sequence with respect to each ith symbol from the last, here a
length of the predetermined sequence being N, and 1.ltoreq.i≦N in
the two slots, and punctures, from the primary basic PRS pattern, a PRS
pattern formed in a location corresponding to a control region, a symbol
axis where a CRS exists, and an reference element (RE) where a PSS, a SSS
and a BCH exist.

9. A transmitting apparatus, comprising: a scrambler to scramble bits
input in a form of code words after channel coding in a downlink; a
modulation mapper to modulate the bits scrambled by the scrambler into a
complex modulation symbol; a layer mapper to map a complex modulation
symbol to one or more transmission layers; a pre-coder to perform
pre-coding of a complex modulation symbol in each transmission channel of
an antenna port; a resource element mapper to map a complex modulation
symbol associated with each antenna port to a corresponding resource
element; and a positioning reference signal (PRS) resource allocator to
divide, into L frequency bands, a total frequency band allocated to a
frequency axis with respect to N consecutive subframes allocated for
transmitting a PRS at regular intervals, and to perform mapping on a
resource element so as to perform muting by not transmitting a PRS to at
least one frequency band with respect to at least one of the N subframes,
and transmitting a PRS to remaining frequency bands.

10. A receiving apparatus, comprising: a reception processing unit to
extract, from a signal received through each antenna port, positioning
reference signals (PRSs) allocated to predetermined resource elements,
through use of a PRS pattern and a muting pattern; a decoder to decode
the extracted PRSs; and a controller to perform controlling so as to
calculate a distance from a cell based on a relative arrival time of the
signal from the cell through use of the decoded PRSs or to transmit the
relative arrival time.

11. A method of transmitting a reference signal, the method comprising
the steps of: selecting a first muting pattern that does not transmit a
positioning reference signal (PRS) in a first frequency-time domain that
is defined by a first frequency domain of a total frequency band
available to a first base station (BS) and a first time domain of a
transmission period of a PRS; transmitting information associated with
the selected first muting pattern to a user equipment (UE); and
generating a PRS based on the first muting pattern and transmitting the
generated PRS.

12. The method as claimed in claim 11, wherein: the first frequency
domain is one or more frequency bands from among frequency bands obtained
by dividing the total frequency band into L frequency bands; and the
first time domain is one or more subframes from among N consecutive
subframes forming the transmission period.

13. The method as claimed in claim 11, wherein the step of transmitting
the information associated with the selected first muting pattern is
performed through use of a higher layer than a layer used for
transmitting the generated PRS.

14. The method as claimed in claim 11, wherein the step of generating and
transmitting the PRS further comprises the steps of: determining a
pattern that transmits a PRS in a second frequency-time domain as opposed
to the first frequency-time domain; and generating a sequence for a PRS
based on the pattern.

15. The method as claimed in claim 11, wherein the first frequency domain
is one of domains obtained by logically dividing the total frequency
domain, and the first frequency domain is physically dispersed into a
frequency axis.

16. The method as claimed in claim 11, wherein the total frequency domain
is divided into L frequency domains and the transmission period is
divided into K periods so that a total frequency-time domain is
distinguished by L×K frequency-time domains, and the first
frequency-time domain includes one or more frequency-time domains from
among the L×K frequency-time domains.

17. The method as claimed in claim 16, wherein: the first BS transmits a
PRS based on the first muting pattern that indicates the first
frequency-time domain among the L×K frequency-time domain; and a
second BS in a neighbor cell of the first BS transmits a PRS based on a
second muting pattern that indicates a second frequency-time domain
including one or more frequency-time domains, different from the first
frequency-time domain, from among the L×K frequency-time domains.

18. A method of receiving a reference signal, the method comprising the
steps of: receiving a first positioning reference signal (PRS) based on a
first muting pattern that does not transmit a PRS in a first
frequency-time domain defined by a first frequency domain and a first
time domain; receiving a second PRS based on a second muting pattern that
does not transmit a PRS in a second frequency-time domain that is
different from the first frequency-time domain; decoding the first PRS
and the second PRS; and performing positioning based on arrival times of
the decoded first PRS and the decoded second PRS.

19. The method as claimed in claim 18, wherein: the first frequency
domain is one or more frequency bands obtained by dividing a total
frequency band into L frequency bands; and the first time domain is one
or more subframes from among N consecutive subframes forming a
transmission period of a PRS.

20. The method as claimed in claim 18, further comprising the step of:
receiving first pattern information associated with the first muting
pattern and second muting pattern information associated with the second
muting pattern.

21. The method as claimed in claim 18, wherein the first frequency domain
is one of domains obtained by logically dividing a total frequency
domain, and the first frequency domain is physically dispersed into a
frequency axis.

22. The method as claimed in claim 18, wherein: a total frequency domain
is divided into L frequency domains and the transmission period is
divided into K periods so that a total frequency-time domain is
distinguished by L×K frequency-time domains; the first
frequency-time domain includes one or more frequency-time domains from
among the L×K frequency-time domains; and the second frequency-time
domain includes one or more frequency-time domains, different from the
first frequency-time domain, from among the L×K frequency-time
domains.

23. An apparatus to transmit a reference signal, the apparatus
comprising: a sequence generator to generate a sequence for a positioning
reference signal (PRS); a resource allocator to allocate a PRS to a
resource element based on a first muting pattern that does not transmit a
PRS in a first frequency-time domain that is defined by a first frequency
domain of an available total frequency band and a first time domain of a
transmission period of a PRS; and a transmitting unit to transmit an
allocated resource through use of a physical channel.

24. The apparatus as claimed in claim 23, wherein: the first frequency
domain is one or more frequency bands from among frequency bands obtained
by dividing the total frequency band into L frequency bands; and the
first time domain is one or more subframes from among N consecutive
subframes forming the transmission period.

25. The apparatus as claimed in claim 24, further comprising: a Radio
Resource Controller (RRC) controller to generate higher layer information
so as to transmit first muting pattern information to a user equipment
(UE).

26. The apparatus as claimed in claim 24, wherein the sequence allocator
determines a pattern that transmits a PRS in a second frequency-time
domain as opposed to the first frequency-time domain, and generates a
sequence for the PRS based on the pattern.

27. The apparatus as claimed in claim 24, wherein the first frequency
domain is one of domains obtained by logically dividing the total
frequency domain, and the first frequency domain is physically dispersed
into a frequency axis.

28. The apparatus as claimed in claim 24, wherein the total frequency
domain is divided into L frequency domains and the transmission period is
divided into K periods so that a total frequency-time domain is
distinguished by L×K frequency-time domains, and the first
frequency-time domain includes one or more frequency-time domains from
among the L×K frequency-time domains.

29. The apparatus as claimed in claim 28, wherein: the transmitting unit
transmits a PRS based on the first muting pattern that indicates the
first frequency-time domain from among the L×K frequency-time
domains; and a base station in a neighbor cell transmits a PRS based on a
second muting pattern that indicates a second frequency-time domain
including one or more frequency-time domains, different from the first
frequency-time domain, from among the L×K frequency-time domain.

30. An apparatus to receive a reference signal, the apparatus comprising:
a receiving unit to receive a first positioning reference signal (PRS)
transmitted based on a first muting pattern that does not transmit a PRS
in a first frequency-time domain defined by a first frequency domain and
a first time domain, and to receive a second PRS transmitted based on a
second muting pattern that does not transmit a PRS in a second
frequency-time domain, different from the first frequency-time domain; a
decoder to decode the first PRS and the second PRS; and a controller to
perform positioning based on arrival times of the decoded first PRS and
the decoded second PRS.

31. The apparatus as claimed in claim 30, wherein: the first frequency
domain is one or more frequency bands from among frequency bands obtained
by dividing a total frequency band into L frequency bands; and the first
time domain is one or more subframes from among N consecutive subframes
forming a transmission period of a PRS.

32. The apparatus as claimed in claim 30, further comprising: a Radio
Resource Controller (RRC) controller to receive first muting pattern
information associated with the first muting pattern and second muting
pattern information associated with the second muting pattern, through
use of a higher layer.

33. The apparatus as claimed in claim 30, wherein the first frequency
domain is one of frequency domains obtained by logically dividing a total
frequency domain, and the first frequency domain is physically dispersed
into a frequency axis.

34. The apparatus as claimed in claim 30, wherein: a total frequency
domain is divided into L frequency domains and the transmission period is
divided into K periods so that the total frequency-time domain is
distinguished by L×K frequency-time domains; the first
frequency-time domain includes one or more frequency-time domains from
among the L×K frequency-time domains; and the second frequency-time
domain includes one or more frequency-time domains, different from the
first frequency-time domain, from among the L×K frequency-time
domains.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is the National Stage Entry of International
Application PCT/KR2010/006808, filed on Oct. 5, 2010, and claims priority
from and the benefit of Korean Patent Application No. 10-2009-0094868,
filed on Oct. 6, 2009, both of which are incorporated herein by reference
for all purposes as if fully set forth herein.

BACKGROUND

[0002] 1. Field

[0003] The present invention relates to a method and apparatus for
transmitting and receiving a signal between a user equipment (UE) and a
base station (BS) in a wireless communication system.

[0004] 2. Discussion of the Background

[0005] As generally known in the art, a positioning method for providing
various location services in Wideband Code Division Multiple Access
(WCDMA) and location information required for communication may be
classified into three methods, that is, a cell coverage-based positioning
method, an observed time difference of arrival-idle period downlink
(OTDOA-IPDL) method, and a network assisted GPS method. The methods do
not compete against one another, but rather complement each other. Each
method may be appropriately utilized for different purposes.

[0006] The OTDOA method may measure relative arrival times of reference
signals (RSs) or pilots transmitted from different base stations (BSs) or
different cells. To calculate a location, a user equipment (UE) or a
mobile station (MS) may need to receive a corresponding RS from at least
three different BSs or Cells. The WCDMA standard may include an idle
period in downlink (IPDL) so as to readily perform the OTDOA location
measurement and to avoid a near-far problem. During the idle period, a UE
or an MS may need to receive an RS or a pilot from a neighbor cell
although an RS or a pilot from a servicing cell where the UE is currently
located is strong.

[0007] A Long Term Evolution (LTE) system, developed from WCDMA that is
associated with the 3GPP, is based on an orthogonal frequency division
multiplexing (OFDM) scheme as opposed to an asynchronous code division
multiple access (CDMA) scheme of WCDMA. In the same manner that WCDMA
performs positioning based on the OTDOA method as described in the
foregoing, a new LTE system considers performing positioning based on the
OTDOA method, and may consider a method that vacates, at regular
intervals, a data region in each subframe structure of one of or both a
multicast broadcast single frequency network (MBSFN) subframes and a
normal subframe, and transmits an RS for positioning to the vacated
region. That is, although positioning in LTE that is an OFDM-based new
generation communication scheme is based on a conventional OTDOA method
in WCDMA, a method of transmitting an RS for positioning in a new
resource allocation structure and a configuration of the RS is required
since a communication basis, such as multiplexing scheme, an access
scheme, and the like, is changed. Also, demand for an accurate
positioning method has been increased due to the development of a
communication system, such as an increase in a movement speed of an UE, a
change in interference environment between BSs, an increase in complexity
of the interference environment, and the like.

SUMMARY

[0008] The present disclosure provides a transceiving method that may
distinguish a positioning reference signal (PRS) based on a frequency
unit for each base station (BS) and thus, may distinguish BSs that
transmit a PRS based on the same PRS pattern, and a system thereof.

[0009] Also, the present disclosure provides a method of performing
grouping on a total frequency band of a BS, and applying different muting
patterns for each grouped frequency band, and a system thereof.

[0010] In order to accomplish the above object, there is provided a method
of transmitting a signal in a wireless communication system, the method
including dividing, into L frequency bands, a total frequency band
allocated to a frequency axis with respect to N consecutive subframes
that are allocated for transmitting a positioning reference signal (PRS)
at regular intervals, and performing muting by not transmitting a PRS to
at least one frequency band with respect to at least one of the N
subframes, and transmitting a PRS to remaining frequency bands.

[0011] In accordance with another aspect of the present invention, there
is provided a transmitting apparatus, including a scrambler to scramble
bits input in a form of code words after channel coding in a downlink, a
modulation mapper to modulate the bits scrambled by the scrambler into a
complex modulation symbol, a layer mapper to map a complex modulation
symbol to one or more transmission layers, a pre-coder to perform
pre-coding of a complex modulation symbol in each transmission channel of
an antenna port, a resource element mapper to map a complex modulation
symbol associated with each antenna port to a corresponding resource
element, and a PRS resource allocator to map a PRS to the resource
element.

[0012] In accordance with still another aspect of the present invention,
there is provided a method of transmitting a reference signal, the method
including selecting a first muting pattern that does not transmit a PRS
in a first frequency-time domain that is defined by a first frequency
domain of a total frequency band available to a base station (BS) and a
first time domain of a transmission period of a PRS, transmitting
information associated with the selected first muting pattern to a user
equipment (UE), and generating a PRS based on the first muting pattern
and transmitting the generated PRS.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a block diagram illustrating a wireless communication
system according to an exemplary embodiment of the present invention.

[0014] FIG. 2 and FIG. 3 are diagrams illustrating patterns of a
positioning reference signal (PRS), which is an example of a reference
signal that is temporarily determined with respect to a single subframe
in a current LTE system, in a case of a normal cyclic prefix (CP) and an
extended CP with respect to a normal subframe.

[0015] FIG. 4 is a diagram illustrating a transmitting apparatus that
generates and transmits a pattern of a PRS according to an exemplary
embodiment of the present invention.

[0016] FIG. 5, FIG. 6, and FIG. 7 are diagrams illustrating a method of
transmitting a PRS based on a muting pattern with respect to an arbitrary
N and K according to another exemplary embodiment of the present
invention.

[0017] FIG. 8 is a diagram illustrating a frequency muting method that
transmits a PRS based on a frequency band-based muting pattern according
to another exemplary embodiment of the present invention.

[0018] FIG. 9 is a diagram illustrating a correlation between logical
frequency division and physical frequency division for frequency muting
that transmits a PRS based on a frequency band-based muting pattern.

[0019] FIG. 10 is a diagram illustrating a frequency muting method that
transmits a PRS based on a frequency band-based muting pattern when L
corresponding to a number of divided frequency bands is 2.

[0020] FIG. 11 is a diagram illustrating a frequency muting method that
transmits a PRS based on a frequency band-based muting pattern when L
corresponding to a number of divided frequency bands is 2.

[0021] FIG. 12, FIG. 13, and FIG. 14 are diagrams illustrating a
hybrid-type based muting method of FIG. 11 when a number of consecutive
PRS subframes allocated for transmitting a PRS is 2, 4, or 6.

[0022] FIG. 15 is a diagram illustrating a frequency muting method that
transmits a PRS based on a frequency band-based muting pattern when L
corresponding to a number of divided frequency bands is 3.

[0023] FIG. 16 is a diagram illustrating a method of transmitting a PRS by
arranging a BS or a cell according to the same muting pattern based on a
single cell-site unit including a plurality of cells according to another
exemplary embodiment of the present invention.

[0024] FIG. 17 is a diagram illustrating a method of transmitting a PRS by
arranging, based on a corresponding muting pattern, a BS or a cell in
each sector or each cell of a single cell-site including a plurality of
cells according to another exemplary embodiment of the present invention.

[0025] FIG. 18 is a block diagram illustrating a user equipment (UE)
according to another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0026] Hereinafter, exemplary embodiments of the present invention will be
described with reference to the accompanying drawings. In the following
description, the same elements will be designated by the same reference
numerals although they are shown in different drawings. Further, in the
following description of the present invention, a detailed description of
known functions and configurations incorporated herein will be omitted
when it may make the subject matter of the present invention rather
unclear.

[0027] In addition, terms, such as first, second, A, B, (a), (b) or the
like may be used herein when describing components of the present
invention. Each of these terminologies is not used to define an essence,
order or sequence of a corresponding component but used merely to
distinguish the corresponding component from other component(s). It
should be noted that if it is described in the specification that one
component is "connected," "coupled" or "joined" to another component, a
third component may be "connected," "coupled," and "joined" between the
first and second components, although the first component may be directly
connected, coupled or joined to the second component.

[0028] FIG. 1 illustrates a wireless communication system according to an
exemplary embodiment of the present invention.

[0029] The wireless communication system is widely installed to provide
various communication services, such as voice data, packet data, and the
like.

[0030] Referring to FIG. 1, the wireless communication system may include
a user equipment (UE) 10 and a base station (BS) 20. The UE 10 and the BS
20 may use various power allocation methods described in the below.

[0031] The UE 10 may be an inclusive concept indicating a user terminal in
a wireless communication, and the concept may include a UE in WCDMA, LIE,
HSPA, and the like, a mobile station (MS), a user terminal (UT), a
subscriber station (SS), a wireless device in GSM, and the like.

[0032] In general, the BS 20 or a cell may refer to a fixed station where
communication with the UE 10 is performed, and may also be referred to as
a Node-B, an evolved Node-B (eNB), a base transceiver system (BTS), an
access point, and the like.

[0033] That is, the BS 20 or the cell may be an inclusive concept
indicating a portion of an area covered by a base station controller
(BSC) in CDMA and a Node B in WCDMA, and the concept may include coverage
areas, such as a megacell, macrocell, a microcell, a picocell, a
femtocell, and the like.

[0034] The UE 10 and the BS 20 are used as two inclusive transceiving
subjects to embody the technology and technical concepts described in the
specifications, and may not be limited to a predetermined term or word.

[0036] Uplink (UL) transmission and downlink (DL) transmission may be
performed based on a time division duplex (TDD) scheme that performs
transmission based on different times, or based on a frequency division
duplex (FDD) scheme that performs transmission based on different
frequencies.

[0037] Exemplary embodiments of the present invention may be applicable to
resource allocation in an asynchronous wireless communication scheme that
is advanced through GSM, WCDMA, and HSPA, to be LTE and LIE-advanced, and
may be applicable to resource allocation in a synchronous wireless
communication scheme that is advanced through CDMA and CDMA-2000, to be
UMB. Exemplary embodiments of the present invention may not be limited to
a specific wireless communication, and may be applicable to all technical
fields to which a technical idea of the present invention is applicable.

[0038] An exemplary embodiment may provide a method of dividing a
frequency resource and a time resource for transmission of a reference
signal (RS) of a UE. Examples of the RS may include a channel state
information reference signal (CSI-RS), a demodulation reference signal
(DM-RS), and the like. In addition, a signal transmitted and received
between a UE and a BS as a reference signal or a standard signal, may be
included. Hereinafter, description will be provided based on a
positioning reference signal (PRS) among the example of the RS.

[0039] FIG. 2 and FIG. 3 illustrate patterns of a PRS, which is an example
of a reference signal that is temporarily determined with respect to a
single subframe in a current LTE system, in a case of a normal cyclic
prefix (CP) and an extended CP with respect to a normal subframe

[0040] 1. A basic PRS pattern is formed in 1/2 of a resource block
including two slots and six subcarriers, based on a predetermined
sequence. An example of the predetermined sequence may be {0, 1, 2, 3, 4,
5}. Also, the two slots may be two time slots forming a positioning
subframe. Here, a method of forming the basic PRS pattern based on the
predetermined sequence may be provided as follows.

[0041] 1-a) When the predetermined sequence f(i)={f(0), f(1), f(2), f(3),
f(4), f(5)}={0, 1, 2, 3, 4, 5}, a PRS pattern is formed in a location of
a subcarrier, on a frequency domain, corresponding to a first value of
the sequence in a last symbol of each of two slots. That is, for the last
symbol, the first value of the sequence is 0 and thus, the PRS pattern is
formed in a location of a zeroth subcarrier. For a second symbol from the
last symbol, a PRS pattern is formed in a location of a subcarrier, on a
frequency domain, corresponding to a second value of the sequence. That
is, for the second symbol from the last symbol, the second value of the
sequence is 1 and thus, the PRS pattern is formed on a location of a
first subcarrier. In the same manner, for each symbol from the last
symbol to a sixth symbol in each of the two slots, a PRS pattern is
formed in a location of a subcarrier, on a frequency domain,
corresponding to a corresponding value of the sequence

[0042] 1-b) A PRS pattern formed in a location corresponding to a control
region such as a physical downlink control channel (PDCCH), a physical
hybrid-ARQ indicator channel (PHICH), and a physical control format
indicator channel (PCFICH), and the like, a symbol axis where a
cell-specific reference signal (CRS) exists, and a reference element (RE)
where a primary synchronization signal (PSS), a secondary synchronization
signal (SSS), and a broadcast channel (BCH) exist, may be punctured from
the basic PRS pattern.

[0043] 1-equation) A process of forming the basic PRS pattern based on
1-a) and 1-b) may be expressed by the following equation.

[0044] v denotes a value defining a location on a frequency domain with
respect to different PRSs, and NsymbDL denotes a total number
of OFDM symbols in each slot in a downlink. In this example, the basic
PRS pattern with respect to a corresponding lth OFDM symbol in each slot
may be formed by Equation 1.

[0045] When a normal CP is used, NsymbDL may be 7, and when an
extended CP is used NsymbDL may be 6. In a case of an even
slot, (ns mod 2) may be 0. In a case of an odd slot, (ns mod 2)
may be 1. Accordingly, in Equation 1, l may be expressed as follows.

[0046] 2. The basic PRS pattern formed in 1/2 of the resource block that
includes two slots forming a single subframe and six subcarriers may be
allocated with respect to a frequency axis up to a system bandwidth, and
with respect to a time axis up to Nsubframe subframes at regular
intervals.

[0047] For example, when the system bandwidth is 10 Mhz, 50 resource
blocks (RBs) exist and thus, the basic PRS pattern formed in 1/2 of the
RB may be repeated as is 100 times with respect to the frequency axis.
When a total number of RBs corresponding to a downlink system bandwidth
is NRBDL, the basic PRS pattern may be repeated
2NRBDL times.

[0048] The basic PRS pattern may be allocated to the Nsubframe subframes
at regular intervals with respect to the time axis. Unlike the frequency
axis, the basic PRS pattern may be allocated to be different for each
system frame number (SFN: a single SFN includes 10 subframes) and for
each piece of cell-specific information, such as, physical cell identity
(PCI) and the like, and the allocation may be time-varying allocation. A
value of defining a location on a frequency domain for PRSs that are
different for each SFN and for the cell-specific information may be
vshift corresponding to a value that is additionally shifted from v
with respect to a frequency axis and thus, a location of a subcarrier
where a PRS is formed in each symbol may be equivalently cyclic-shifted
by vshift.

[0049] When the step 2 is applied to a Kth subcarrier in a total system
bandwidth including NRBDLNscRB subcarriers, it may be
expressed by Equation 2. In this example, NRBDL denotes a total
number of RBs corresponding to a downlink system bandwidth,
NscRB denotes a number of subcarriers in a single RB, and a
normal subframe that is configured to be a positioning subframe may be
based on Equation 2.

k=6m+(v+vshift)mod 6

m=0, 1, . . . , 2NRBDL-1 [Equation 2]

[0050] Here, a value that defines a location on a frequency domain for the
different PRSs may be v as described in the step 1, vshift may be a
value to equivalently cyclic-shift a location of a subcarrier where a PRS
is formed in each symbol based on a SFN and cell-specific information. In
this example, vshift may correspond to a remainder obtained when a
value generated based on a function of an SFN and cell-specific
information is divided by an available total frequency shift value, 6.
Particularly, at least one pseudo-random sequence value may be obtained
from a pseudo-random sequence that is generated using cell-specific
information, such as a PCI, as an initial value, through use of a
function including a positioning SFN. The obtained at least one
pseudo-random sequence value may be multiplied by a constant, the at
least one multiplied value may be added up, and the sum may be divided by
the available total frequency shift value, 6, so as to obtain the
remainder. This may be expressed by Equation 3.

[0051] Here, 0≦NCellID<504 denotes a physical cell ID
(PCI), a denotes a constant, c(i) denotes a pseudo-random sequence, and
an initial value of c is cinit=NCellID and it may be
initialized for each subframe for positioning.

[0052] The step 1 and the step 2 may be expressed by an equation as
follows.

[0053] That is, a PRS sequence rl,ns(m) mapped to a
complex-valued modulation symbol ak,l.sup.(p) that is used as a
positioning reference symbol for an antenna port p in nsth slot, may
be expressed by Equation 4.

[0055] In this example, v and vshift that are values of defining
locations on a frequency domain for different PRSs may be expressed by
Equation 5. Particularly, vshift may be a value specialized for a
cell-specific and a positioning SFN.

[0056] In Equation 5, nsubframe denotes a positioning SFN, and an
initial value of c in pseudo-random sequence c(i) is
cinit=NCellID and the initival value may be initialized
for each subframe for positioning.

[0057] FIG. 4 illustrates a transmitting apparatus that generates and
transmits a pattern of a PRS according to an exemplary embodiment of the
present invention.

[0058] Referring to FIG. 4, a transmitting apparatus 400 that generates
and transmits a pattern of a PRS may include a sequence generator 410 and
a PRS resource allocator 420. The sequence generator 410 may generate a
sequence for a PRS as described in the foregoing. The PRS resource
allocator 420 may allocate PRSs to resource elements based on the PRS
sequence generated by the sequence generator 110 according to a PRS
pattern and a muting pattern. Subsequently, the PRSs allocated to the
resource elements may be multiplexed with a BS transmission frame. Here,
the PRS pattern may be a PRS transmission pattern that is defined within
a single subframe, and the muting pattern may be a subframe-based PRS
transmission pattern in which a PRS pattern is basically defined.

[0059] The PRS resource allocator 420 may allocate a resource associated
with an OFDM symbol (x-axis) and a location of a subcarrier (y-axis)
based on a predetermined rule so as to allocate a resource for a PRS, and
may multiplex the allocated resource with a BS transmission frame at a
predetermined frame timing.

[0060] Hereinafter, a signal generating structure of a downlink physical
channel of a wireless communication system will be described with
reference to FIG. 4. The signal generating structure of the downlink
physical channel of the wireless communication system may omit, replace
or change elements, and may add other elements.

[0061] Bits input in a form of code words after channel coding in a
downlink may be scrambled by a scrambler, and may be input to a
modulation mapper. The modulation mapper may modulate the scrambled bits
into a complex modulation symbol. A layer mapper may map the complex
modulation symbol to one or more transmission layers. Subsequently, a
pre-coder may perform pre-coding of a complex modulation symbol in each
transmission channel of an antenna port. Subsequently, a resource element
mapper may map a complex modulation symbol with respect to each antenna
port to a corresponding resource element. The PRS resource allocator 420
may form a PRS pattern based on the sequence generated by the sequence
generator 410, and may perform mapping of a PRS.

[0062] That is, the PRS resource allocator 420 may allocate a PRS that is
generated based on a predetermined PRS sequence after going through at
least one of the described devices, to resource elements corresponding to
resources where a predetermined OFDM symbol (time-axis) and a subcarrier
(frequency-axis) are located, based on a PRS pattern generated based on
the sequence, and may multiplex the allocated PRS with a BS transmission
frame at a predetermined frame timing.

[0063] In this example, existing reference signals (RSs), control signals,
and data input from the pre-coder may be allocated by the resource
element mapper to resource elements corresponding to resources where a
predetermined OFDM symbol (time-axis) and a subcarrier (frequency-axis)
are located. Here, a device that provides an additional function
(generating of a PRS pattern and mapping of a PRS) to the resource
element mapper so as to allocate a PRS to a corresponding resource
element, may correspond to a PRS mapping unit.

[0064] Subsequently, the OFDM signal generator may generate a complex time
domain OFDM signal for each antenna. The complex time domain OFDM signal
may be transmitted through an antenna port.

[0065] As illustrated in FIG. 3 and FIG. 4, a PRS pattern with respect to
a single subframe and one RB along a frequency axis may be copied and
transmitted up to a system bandwidth with respect to the frequency axis,
and may be transmitted at regular intervals, such as 160 ms (160
subframes), 320 ms (320 subframes), 640 ms (640 subframes), or 1280 ms
(1280 subframes), with a predetermined offset with respect to a time
axis, through use of consecutive subframes, such as 1 subframe, 2
subframes, 4 subframes, or 6 subframes. In this example, in each BS 20, a
bandwidth associated with a frequency axis for a PRS, a period of a
subframe used for transmission of a PRS and an offset associated with a
time axis, and a number of consecutive subframes used for transmission of
a PRS may be controlled by a higher layer, and the information may be
transmitted to each UE 10 through a higher layer, for example, a radio
resource controller (RRC). In this example, the offset period, the number
of allocated subframes, and the like used in the PRS pattern are merely
examples, and may be variously changed.

[0066] In this example, a cell-specific subframe configuration period
(TPRS) for transmission of a PRS may be 160, 320, 640, and 1280
subframes, and a cell-specific subframe offset may be [IPRS], [IPRS-160],
[IPRS-480], and [IPRS-1120]. In this example, the PRS configuration index
IPRS may be determined by a higher layer.

[0067] A PRS to be used for estimating a location of a user may be
transmitted during a predetermined time unit. For more accurate
positioning, a time variant pattern or a time non-variant pattern may be
transmitted during twice an amount of the determined time. For example,
when 1 subframe is a minimum unit for transmitting a PRS, PRSs may be
transmitted through 2, 3, 4, . . . , N subframes. In this example, when a
pattern of a PRS transmitted to each subframe is a time non-varying
pattern, the pattern may be the same for each subframe. When the pattern
is time varying pattern, the pattern may be different for each subframe.

[0068] Specifically, as illustrated in FIG. 3 and FIG. 4, when a PRS
pattern is cyclic-shifted with respect to the frequency axis, a number of
distinguished patterns may be 6. Accordingly, BSs 20 may be classified
into 6 groups, and each group may perform transmission based on different
PRS patterns. However, when it is assumed that BSs 20 within Tier 2 based
on the UE 10 are considered (here, although BSs beyond Tier 2 transmit
PRSs, a signal to the corresponding UE is weak and thus, BSs from which
the UE substantially receives signals are considered to be BSs within
Tier 2), BSs 20 corresponding to 19 cell sites or 57 cells may exist and
thus, the BSs 20 within Tier 2 may not be able to transmit PRSs having
different patterns for each BS through use of the 6 PRS patterns. Also, a
plurality of BSs 20 having the same PRS pattern may exist and inter-cell
interference may occur that prevent distinguishing all PRSs transmitted
from neighbor BSs during PRS transmission between BSs and thus,
performance may be deteriorated. In this communication environment,
interference may occur among cells using the same PRS pattern and thus,
the accurate detection of a PRS may be difficult and a number of detected
cells may be decreased.

[0069] When a PRS is transmitted based on at least a minimum time unit,
that is, when a PRS is transmitted based on at least one subframe, PRSs
may be transmitted to all the determined N subframes. Also, a
predetermined BS 20 may not transmit a PRS. Accordingly, interference
occurring when PRSs are transmitted among BSs may be reduced and thus,
performance may be improved.

[0070] To reduce interference of a PRS, a BS may select a first muting
pattern that does not transmit a PRS in a first frequency-time domain
defined by a first frequency domain of an available total frequency band
and a first time domain of a transmission period of a PRS, may share
first muting pattern information with a UE through an RRC and the like,
and may generate and transmit a PRS based on the first muting pattern.

[0071] Particularly, a total frequency domain is divided into L frequency
domains and the transmission period is divided into K periods so that a
total frequency-time domain may be distinguished by L×K
frequency-time domains, and the first frequency-time domain may include
one or more frequency-time domains from among the L×K
frequency-time domains.

[0072] Also, the first muting pattern may denote the first frequency-time
domain from among the L×K frequency-time domains, the BS may
transmit a PRS based on the first muting pattern, and a second BS in a
neighbor cell of the BS may transmit a PRS based on a second muting
pattern indicating a second frequency-time domain including one or more
frequency-time domains, different from the first frequency-time domain,
from among the L×K frequency-time domains and thus, a probability
that PRSs of the BSs interfere with each other may be decreased.

[0073] The PRS pattern as described with reference to FIG. 2 may be a PRS
pattern that performs transmission in the second frequency-time domain as
opposed to the first frequency-time domain. That is, the first
frequency-time domain may be a domain that does not transmit a PRS and
thus, the second frequency-time domain may transmit a PRS. Also, a
sequence for a PRS may be generated based on a PRS pattern (when a PRS is
transmitted within a subframe.

[0074] FIG. 5, FIG. 6, and FIG. 7 illustrate a method of transmitting a
PRS based on a muting pattern with respect to an arbitrary N and K
according to another exemplary embodiment of the present invention. FIG.
5 illustrates a method of transmitting a PRS based on a general muting
pattern. FIG. 6 illustrates a method of transmitting a PRS based on a
muting pattern when N=3, K=1, and a number of cell groups (M)=3. FIG. 7
illustrates a method of transmitting a PRS based on a muting pattern when
N=4, K=2, and M=6. Here, M may correspond to a number of total cell
groups including persistent muting cell groups that perform muting by not
transmitting a PRS with respect to all N subframes allocated for
transmitting a PRS during a predetermined period.

[0075] Referring to FIG. 5, FIG. 6, and FIG. 7, when subframes are
allocated for transmitting a PRS during subframes from zeroth to N-lth
subframe, transmission may be performed by dividing the subframes into
`Transmit` subframe sections that transmit a PRS and `mute` subframe
sections that do not transmit a PRS.

[0076] That is, N (N=1, 2, 4, or 6) consecutive subframes may be allocated
for transmitting a PRS at regular intervals (160 ms, 320 ms, 640 ms, or
1280 ms, a single subframe corresponding to 1 ms), and each BS 20 or cell
group may transmit a PRS to K subframes (`transmit` subframes) from among
the N subframes, and may perform muting N-K subframes by not transmitting
a PRS to N-K subframes (`Mute` subframes). In this example, a PRS pattern
associated with the K subframes that transmit a PRS and the N-K subframes
that perform muting by not transmitting a PRS may be copied and
transmitted up to a system bandwidth for a PRS with respect to a
frequency axis.

[0077] A time when a PRS is transmitted for each BS may be additionally
distinguished based on a subframe unit so that BSs that transmit a PRS
based on the same PRS pattern may be distinguished. In this manner, by
taking into consideration effects from interference occurring among BSs
and a local characteristic of a BS, more excellent performance may be
obtained than by using a scheme that transmits a PRS to all subframes.
That is, when subframes that transmit a PRS are adjusted by applying a
muting pattern, a limited number of PRS patterns may be increased and
interference caused by neighbor cells may be reduced. Therefore, the
limited PRS patterns may have diversity and thus, an accuracy of
positioning may be expected to be improved.

[0078] The muting pattern expressed in FIG. 5, FIG. 6, and FIG. 7 may
provide an effect of increasing a number of basic PRS patterns, which is
relatively limited.

[0079] In this example, the UE 10 may require additional information since
the UE 10 may need to be aware of a muting pattern used by each cell. The
UE 20 may need information associated with a time-offset of a serving
cell and measured cells, a cell ID, and the like. In particular,
secondary data associated with the serving cell may include a bandwidth
for PRSs, a PRS configuration index, and a number of consecutive downlink
subframes NPRS. Secondary data associated with the measured cell may
include a PCI, a timing offset, a normal or extended CP, an antenna port
configuration, and a slot number offset.

[0080] The muting pattern may be cell-specific information and thus,
muting pattern information of both the serving cell and the measured cell
may need to be broadcasted to the target UE 10 through a higher layer
signaling. The muting pattern may select K subframes from among the N
consecutive PRS subframes for transmission of a PRS. In this example, a
number of available selections may be M, and M=NCK(K=.left
brkt-bot.N/2.right brkt-bot. or .left brkt-top.N/2.right brkt-bot.).

[0081] Accordingly, bits to be additionally provided to the UE 10 through
the higher layer signaling may be .left brkt-top.log2M.right
brkt-bot. per cell. For example, N=3, K=1, and M=3 and thus, the
transmission of additional information of .left brkt-top.log23.right
brkt-bot.=2 bit per cell may be required. When a number of service cells
and measured cells is 57 (at least Tier 2 in the 3-sector cell
environment), additional information of 2×57=114 bits may be
required to transmitted to the target UE 10. Referring to FIG. 7, N=4,
K=2, and M=6, and thus, additional bits per cell may be 3 bits. When the
number of the serving cells and the measured cells is 57, additional
information of 171 bits may be required to be transmitted to the target
UE 10. Accordingly, as a number of the consecutive PRS subframes (N)
increases, K proportionally increases. As K increases, a total number of
muting patterns (M) also increases. Accordingly, information to be
broadcasted by each cell may be rapidly increased.

[0082] The muting pattern may be formed as shown in the combination of
FIG. 7 based on set K. Referring to FIG. 7, a number of muting patterns
is 6, and when the muting pattern is combined with a basic PRS pattern,
36 combined PRS-muting patterns may be formed. However, a number of
orthogonal patterns is not substantially increased due to interference
caused by measured cells for each subframe. Inter-cell interference may
be decreased by about 1/2, as shown in FIG. 7.

[0083] The PRS pattern may be allocated to a basically given total
bandwidth and thus, a frequency-diversity may be sufficiently obtained by
applying a muting pattern. However, time-axis transmission, corresponding
to a number of subframes that perform muting on the all subframes
allocated for transmitting a PRS by not transmitting a PRS to the all
subframes, may not be performed and thus, a time-diversity may be
insufficiently obtained.

[0084] Hereinafter, a frequency band-based muting method for transmitting
a PRS will be described according to another exemplary embodiment. The
other exemplary embodiment may configure a muting pattern through simple
division of a frequency band, and may reduce a number of cells that use
the same resource so as to effectively reduce inter-cell interference.

[0085] FIG. 8 illustrates a frequency muting method that transmits a PRS
based on a frequency band-based muting pattern according to another
exemplary embodiment of the present invention.

[0086] Referring to FIG. 8, each BS group may divide, into L frequency
bands, the total frequency band allocated to a wireless communication
system along a frequency axis with respect to N (N=1, 2, 4, or 6)
consecutive subframes that are allocated for transmitting a PRS at
regular intervals (160 ms, 320 ms, 640 ms, or 1280 ms, a single subframe
corresponding to 1 ms), may transmit a PRS to at least one predetermined
frequency band, and may perform muting by not transmitting a PRS to
remaining frequency bands.

[0087] FIG. 9 illustrates a correlation between logical frequency division
and physical frequency division for frequency muting that transmits a PRS
based on a frequency band-based muting pattern.

[0088] Division of a frequency band may not always indicate physical
division of a frequency. The division of a frequency band may include a
logical division of a frequency or a channel as illustrated in FIG. 9.
Accordingly, the logical frequency division may be the same as the
physical frequency division, or may be different from the physical
frequency division.

[0089] Referring to FIG. 9, when a frequency band is divided into L
frequency bands (F0 through FL-1) based on a logical frequency division,
a predetermined frequency band, for example, a frequency band F0 may be
physically dispersed into a frequency axis as illustrated on the right of
FIG. 9.

[0090] By taking into consideration an arrangement of cells in the
dispersed frequency bands, a PRS may be transmitted only to at least one
predetermined frequency band, and a PRS may not be transmitted to
remaining frequency bands so that the remaining frequency bands may be
muted and thus, inter-cell interference may be reduced. At the same time,
transmission may be continuously performed in a time-domain and thus, a
sufficient time-diversity may be obtained during a consecutive PRS
subframe section defined for transmission of a PRS.

[0091] Also, physical locations of PRSs or a density per unit area may not
be changed by applying the frequency muting described in the foregoing
with reference to FIG. 5, FIG. 6, FIG. 7, and FIG. 8 and thus, a
measurement error caused by a change in a physical location of a PRS or a
reduced density, which may be used for time muting that is described with
reference to FIG. 5, FIG. 6, and FIG. 7, may not occur. Also, a
hybrid-type that sufficiently obtains a frequency-diversity through
alternate allocation to the divided frequency bands, may be readily
defined and thus, it may be readily introduced in a multi-cell
environment.

[0092] According to another exemplary embodiment, although L corresponding
to a number of divided frequency bands may not be limited, the number of
divided bands may be adjusted based on a length of a pseudo-random
sequence associated with a requirement of a wireless communication
system.

[0093] Hereinafter, although a total frequency band is divided into two or
three frequency bands for ease of description, the number of divided
frequency bands may not be limited thereto.

[0094] FIG. 10 illustrates a frequency muting method that transmits a PRS
based on a frequency band-based muting pattern when L corresponding to a
number of divided frequency bands is 2.

[0095] Referring to FIG. 10, a total frequency band allocated to a
wireless communication system along a frequency axis with respect to N
(N=1, 2, 4, or 6) consecutive subframes allocated for transmitting a PRS
at regular intervals (160 ms, 320 ms, 640 ms, or 1280 ms, a single
subframe corresponding to 1 ms) may be divided into two frequency bands.
In this example, an even frequency-band in the two frequency bands may
correspond to a lower frequency band (F1), and an odd frequency-band in
the two frequency bands may correspond to the remaining higher frequency
band (F0).

[0096] The wireless communication system may group the BSs into three BS
groups, that is, cell groups 1 through 3. The cell group 1 may transmit a
PRS to the odd frequency band (F0) from among the total frequency band
allocated to the wireless communication system along the frequency axis
with respect to the N (N=1, 2, 4, or 6) consecutive subframes, and may
mute the even frequency band (F1) by not transmitting a PRS to the even
frequency band (F1).

[0097] The cell group 2 may transmit a PRS to the even frequency band (F1)
from among the total frequency band allocated to the wireless
communication system along the frequency axis with respect to the N (N=1,
2, 4, or 6) consecutive subframes, and may mute the odd frequency band
(F0) by not transmitting a PRS to the odd frequency band (F0).

[0098] The cell group 3 may transmit a PRS to the total frequency band
allocated to the wireless communication system along the frequency axis
with respect to the N (N=1, 2, 4, or 6) consecutive subframes, that is,
both the odd frequency band (F0) and the even frequency band (F1). In
this example, the cell group 3 may mute the total frequency band by not
transmitting a PRS to the total frequency band allocated to the wireless
communication system along the frequency axis.

[0099] A PRS may be distinguished by dividing, into two frequency bands,
the total frequency band allocated to the wireless communication system
along the frequency axis with respect to the N (N=1, 2, 4, or 6)
consecutive subframes that are allocated for transmitting a PRS at
regular intervals, and by grouping the BSs into three groups.
Accordingly, since a number of BSs distinguished with respect to a time
and a frequency is determined to be 6 based on different PRS patterns,
BSs 20 may be distinguished in a total of 18 ways.

[0100] Although a PRS is transmitted by distinguishing BSs based on the
method of FIG. 10, each BS uses a predetermined frequency band and thus,
a performance may be deteriorated in association with frequency band.

[0101] FIG. 11 illustrates a frequency muting method that transmits a PRS
based on a frequency band-based muting pattern when L corresponding to a
number of divided frequency bands is 2.

[0102] Referring to FIG. 11, a total frequency band allocated to a
wireless communication system along a frequency axis with respect to N
consecutive subframes that are allocated for transmitting a PRS at
regular intervals may be divided into two frequency bands.

[0103] The wireless communication system may group BSs into three BSs
group, that is, cell groups 1 through 3. Based on a two-subframe unit,
the cell group 1 (M_pattern=0) may transmit a PRS in an odd subframe,
such as, a first subframe, a third subframe, and the like, of an odd
frequency band (F0) from among the N consecutive subframes, and may mute
an even subframe, such as, a second subframe, a fourth subframe, and the
like, by not transmitting a PRS or transmitting a PRS with zero (0)
power. Also, the cell group 1 may transmit a PRS in an even subframe of
an even frequency band (F1) and may mute an odd subframe by not
transmitting a PRS or transmitting a PRS with zero (0) power. In FIG. 11,
the odd subframes may be subframe #0, #2, and the like, and the even
subframes may be subframes #1, #3, and the like. Throughout the
specification, an odd/even subframe according to an exemplary embodiment
may correspond to the above configuration.

[0104] Conversely, based on a two-subframe unit, the cell group 2
(M_pattern=1) may transmit a PRS in the even subframe of the odd
frequency band (F0) from among the N consecutive subframes, and may mute
the odd subframe by not transmitting a PRS or transmitting a PRS with
zero (0) power. Also, the cell group 2 may transmit a PRS in the odd
subframe of the even frequency band (F1), and may mute an even subframe
by not transmitting a PRS or transmitting a PRS with zero (0) power.

[0105] The cell group 3 (none of muting) may transmit a PRS to the total
frequency band allocated to the wireless communication system along the
frequency axis with respect to the N consecutive subframes, that is, both
the odd frequency band (F0) and the even frequency band (F1). In this
example, the cell group 3 may mute the total frequency band allocated to
the wireless communication system along the frequency axis by not
transmitting a PRS.

[0106] The basic pattern of FIG. 11 may be repeated based on a
two-subframe unit, and a basic pattern based on a subframe unit may also
be configurable.

[0107] A PRS may be transmitted by distinguishing BSs based on the method
of FIG. 11 and thus, a frequency band that transmits a PRS is different
for each subframe. Accordingly, the method FIG. 11 is an advanced
structure when compared to the method of FIG. 9. The method of FIG. 9 may
transmit a PRS through a total frequency band and thus, a
frequency-diversity and a time-diversity may be simultaneously obtained.

[0108] In the current LTE system, a PRS with respect to a single subframe
and one RB along a frequency axis may be transmitted at regular
intervals, such as 160 ms (160 subframes), 320 ms (320 subframes), 640 ms
(640 subframes), or 1280 ms (1280 subframes), with a predetermined offset
with respect to a time axis, through use of consecutive subframes, such
as 1 subframe, 2 subframes, 4 subframes, or 6 subframes. In terms of the
above standard, the transmission subframes for all types of PRSs may be
covered by repeating the two-subframe based muting pattern described in
the foregoing with reference to FIG. 8 or FIG. 9.

[0109] FIG. 12, FIG. 13, FIG. 14 illustrate a hybrid-type based muting
method of FIG. 11 when a number of consecutive PRS subframes allocated
for transmitting a PRS is 2, 4, or 6.

[0110] Referring to FIG. 12, FIG. 13, and FIG. 14, a total frequency band
allocated to a wireless communication system along a frequency axis with
respect to N consecutive subframes that are allocated for transmitting a
PRS at regular intervals may be divided into two frequency bands.

[0111] The wireless communication system may group BSs into three BS
groups, that is, cell groups 1 through 3. Based on a two-subframe unit,
the cell group 1 (M_pattern=0) may transmit a PRS in an odd subframe of
an odd frequency band (F0) and in an even subframe of an even frequency
band (F1) from among the N consecutive subframes, and may mute remaining
subframes by not transmitting a PRS.

[0112] Conversely, based on a two-subframe unit, the cell group 2
(M_pattern=1) may transmit a PRS in an even subframe of the odd frequency
band (F0) and in an odd subframe of the even frequency band (F1) from
among the N consecutive subframes, and may mute remaining subframes by
not transmitting a PRS.

[0113] The cell group 3 (none of muting) may transmit a PRS to the total
frequency band allocated to the wireless communication system along the
frequency axis with respect to the N consecutive subframes, or may mute
the total frequency band by not transmitting a PRS.

[0114] As described in the foregoing with reference to FIG. 12, FIG. 13,
and FIG. 14, the wireless communication system divides the allocated
total frequency band into two frequency bands and repeat a frequency
muting pattern based on a two-subframe unit and thus, may use the same
frequency muting pattern irrespective of a number of consecutive
subframes (M).

[0115] FIG. 15 illustrates a frequency muting method that transmits a PRS
based on a frequency band-based muting pattern when L corresponding to a
number of divided frequency bands is 3.

[0116] Referring to FIG. 15, a total frequency band allocated to a
wireless communication system along a frequency axis with respect to N
consecutive subframes that are allocated for transmitting a PRS at
regular intervals may be divided into three frequency bands.

[0117] The wireless communication system may group BSs into four BSs, that
is, cell groups 1 through 4. Based on a three-subframe unit, the cell
group 1 (M_pattern=0) may transmit a PRS in a first subframe (subframe
#0) of a first frequency band (F0) from among the N consecutive
subframes, and may mute second and third subframes (subframes #1 and #2)
by not transmitting a PRS or transmitting a PRS with zero (0) power.
Also, the cell group 1 may transmit a PRS in a second subframe (subframe
#1) of a second frequency band (F1), and may mute first and third
subframes (subframes #0 and #2) by not transmitting a PRS or transmitting
a PRS with zero (0) power. Also, the cell group 1 may transmit a PRS in a
third subframe (subframe #2) of a third frequency band (F2), and may mute
first and second subframes (subframes #0 and #1) by not transmitting a
PRS or transmitting a PRS with zero (0) power.

[0118] Based on a three-subframe unit, the cell group 2 (M_pattern=1) may
transmit a PRS in the third subframe (subframe #2) of the first frequency
band (F0), the first subframe (subframe #0) of the second frequency band
(F1), and the second subframe (subframe #1) of the third frequency band
(F2), and may mute remaining subframes by not transmitting a PRS or
transmitting a PRS with zero (0) power.

[0119] Based on a three-subframe unit, the cell group 3 (M_pattern=4) may
transmit a PRS in the second subframe (subframe #1) of the first
frequency band (F0), the third subframe (subframe #2) of the second
frequency band (f1), and the first subframe (subframe #0) of the third
frequency band (F2), and may mute remaining subframes by not transmitting
a PRS or transmitting a PRS with zero (0) power.

[0120] The cell group 4 (none of muting) may transmit a PRS to the total
frequency band allocated to the wireless communication system along the
frequency axis with respect to the N consecutive subframes, that is, the
odd frequency band (F0) and the even frequency band (F0). In this
example, the cell group 4 may mute the total frequency band allocated to
the wireless communication system along the frequency axis by not
transmitting a PRS.

[0121] The transmission subframes for a PRS when a number of consecutive
PRS subframes N is 3 or 6 may be covered by repeating the three-subframe
based muting pattern as described with reference to FIG. 15.

[0122] A downdrift in inter-cell interference of a muting pattern may vary
based on a multi-cell arrangement. Hereinafter, a method of allocating a
muting pattern to a single cell-site including a plurality of cells in a
wireless communication environment will be described.

[0123] Examples of PRS transmission or muting that is patterned based on a
frequency and a time in a form of a grid have been provided in the
foregoing with reference to FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG.
10, FIG. 11, FIG. 12, FIG. 13, FIG. 14, and FIG. 15. In particular, a
time domain having a transmission period of a PRS as an axis and a
frequency domain having an available total frequency as an axis may be
divided. A pattern (muting pattern) associated with a domain that
performs muting from among the divided domains may be shared between a BS
and a UE, and the BS may transmit a PRS based on the muting pattern. BSs
in neighbor cells may transmit a PRS based on another muting pattern that
performs muting in domains that are partially or completely different
from the domain indicated by the muting pattern. Accordingly, the UE may
receive a PRS from one or a few BSs in a frequency-time domain muted
based on a muting pattern and thus, interference may be reduced.

[0124] FIG. 16 illustrates a method of transmitting a PRS by arranging a
BS or a cell according to the same muting pattern based on a single
cell-site unit including a plurality of cells according to another
exemplary embodiment of the present invention.

[0125] The cell-site may be defined based on a plurality of cells or a
plurality of sectors. In a wireless communication environment configured
by assuming a general 3-sector antenna, three cells or sectors may
configure a single cell-site. For examples, three cells or sectors, such
as cell 0 through cell 2, cell 3 through cell 5, and the like, may
configure a single cell-site.

[0126] In the wireless communication environment, BSs (cells) may be
arranged according to the same muting pattern based on a single cell-site
unit including the three cells, or cells may be designed to have the same
muting pattern in the same cell-site, through use of Equation 6.

[0127] Here, vshift denotes a parameter to generate different PRS
patterns as described in FIG. 2 and FIG. 3. Generated frequency muting
patterns may be M_pattern 0 (mpattern=0) and M_pattern 1
(mpattern=1). In this example, the multi-cell arrangement may be
represented as shown in FIG. 14.

[0128] FIG. 17 illustrates a method of transmitting a PRS by arranging,
based on a corresponding muting pattern, a BS or a cell in each sector or
each cell of a single cell-site including a plurality of cells according
to another exemplary embodiment of the present invention.

[0129] In the wireless communication environment as shown in FIG. 16, a
few cells in a single cell-site including three cells may be designed to
have the same muting pattern or to have different muting patterns from
each other, through use of Equation 7.

[0130] Here, vshift denotes a parameter to generate different PRS
patterns as illustrated in FIG. 2 and FIG. 3. Two frequency muting
patterns may be provided in total and generated frequency muting patterns
may be M_pattern 0 (mpattern=0) and M_pattern 1 (mpattern=1).
In this example, a multi-cell arrangement may be represented as shown in
FIG. 15.

[0131] Referring to FIG. 17, a few cells may have the same muting
patterns, or may have the different muting patterns from each other in
the single cell-site.

[0132] In this example, in each BS 20, a bandwidth associated with a
frequency axis for a PRS, a period of a subframe used for transmission of
a PRS and an offset associated with a time axis, and a number of
consecutive subframes used for transmission of a PRS may be controlled by
a higher layer, and the information may be transmitted to each UE 10
through a higher layer, for example, an RRC.

[0133] In this example, a number of cell groups (M), a number of cells per
group or a length of consecutive PRS subframes that perform transmission
as opposed to performing muting from among the allocated N consecutive
subframes (k), and a number of frequency bands obtained by dividing the
total frequency band allocated to the wireless communication system along
a frequency axis (L) may be optimally selected by a BS 20 or core
network.

[0134] The frequency band-based muting method for PRS transmission
according to the exemplary embodiment may configure different muting
patterns for PRSs by simply dividing a frequency band, and may reduce a
number of cells using the same resource in a frequency and thus,
inter-cell interference may be efficiently reduced.

[0135] The frequency band-based muting method for PRS transmission
according to the exemplary embodiment may be readily applied irrespective
of a number of subframes that transmit consecutive PRSs during a
predetermined period and thus, transmission of additional information may
not be required in a network or sufficient information may be transferred
through use of at most 1 bit of additional information per cell. That is,
additional secondary data of a higher layer, such as L2, L3, and the
like, may not be required or an OTDOA-based positioning method may be
efficiently managed through use of at most 1 bit.

[0136] FIG. 18 illustrates a UE according to another exemplary embodiment
of the present invention.

[0137] Referring to FIG. 18, a receiving apparatus 1300 of the UE 10 may
include a reception processing unit 1310, a decoder 1320, and a
controller 1330.

[0138] The reception processing unit 1310 may receive, from at least three
different BSs 20, PRSs of which PRS patterns and muting patterns are
different from each other.

[0139] The decoder 1320 may recognize a muting pattern of each cell and
may decode a PRS based on a general positioning scheme. The decoder 1320
may decode the received PRSs of which PRS patterns and muting patterns
are different from each other, the PRS being received by the reception
processing unit 1310 from the at least three different BSs 20.

[0140] The controller 1330 may estimate a distance from each BS 20 based
on relative arrival times of the PRSs that are received from the at least
three different BSs 20 and are decoded by the decoder 1320, according to
the OTDOA method, and may estimate its location based on a triangulation
method.

[0141] Hereinafter, the operations of the receiving apparatus 1300 of the
UE 10 for positioning will be described.

[0142] A signal received through each antenna port may be converted into a
complex time domain signal by the reception processing unit 1310. Also,
the reception processing unit 1310 may extract PRSs allocated to
predetermined resource elements, from the received signal based on a PRS
pattern and a muting pattern. The decoder 1312 may decode the extracted
PRSs. The controller 1014 may measure a distance from a BS 20 based on a
relative arrival time from the BS 20, through use of information
associated with the decoded PRSs. In this example, the controller 1014
may calculate a distance from the BS 20 based on the relative arrival
time from the BS 20, or the controller 1014 may transmit the relative
arrival time to the BS 20 so that the BS 20 may calculate the distance.
In this example, distances from the at least three BSs 20 may be measured
and thus, the location of the UE 10 may be calculated.

[0143] The receiving apparatus 1300 may correspond to the wireless
communication system or the transmitting apparatus 400 described with
reference to FIG. 4 and thus, may receive a signal transmitted from the
transmitting apparatus 400. Accordingly, the receiving apparatus 1300 may
be configured of elements for reversely performing a signal processing of
the transmitting apparatus 400. Therefore, elements of the receiving
apparatus 1300 that are not described in detail may be understood to be
replaced with elements for reversely performing a signal processing of
the transmitting apparatus 400.

[0144] That is, operations of a UE may include receiving a first PRS
transmitted based on a first muting pattern that does not transmit a PRS
in a first frequency-time domain defined by a first frequency domain and
a first time domain, receiving a second PRS transmitted based on a second
muting pattern that does not transmit a PRS in a second frequency-time
domain, different from the first frequency-time domain, decoding the
first PRS and the second PRS, and performing positioning based on arrival
times of the decoded first PRS and second PRS. Also, the UE may further
receive a PRS for positioning.

[0145] First muting pattern information associated with the first muting
pattern and second muting pattern information associated with the second
muting pattern may be received from a BS through use of a higher layer,
to receive/decode each PRS and to determine an arrival time.

[0146] In addition, since terms, such as "including," "comprising," and
"having" mean that one or more corresponding components may exist unless
they are specifically described to the contrary, it shall be construed
that one or more other components can be included. All of the
terminologies containing one or more technical or scientific
terminologies have the same meanings that persons skilled in the art
understand ordinarily unless they are not defined otherwise. A term
ordinarily used like that defined by a dictionary shall be construed that
it has a meaning equal to that in the context of a related description,
and shall not be construed in an ideal or excessively formal meaning
unless it is clearly defined in the present specification.

[0147] Although a preferred embodiment of the present invention has been
described for illustrative purposes, those skilled in the art will
appreciate that various modifications, additions and substitutions are
possible, without departing from the scope and spirit of the invention as
disclosed in the accompanying claims. Therefore, the embodiments
disclosed in the present invention are intended to illustrate the scope
of the technical idea of the present invention, and the scope of the
present invention is not limited by the embodiment. The scope of the
present invention shall be construed on the basis of the accompanying
claims in such a manner that all of the technical ideas included within
the scope equivalent to the claims belong to the present invention.

Patent applications by Kibum Kwon, Ansan-Si KR

Patent applications by Kitae Kim, Suwon-Si KR

Patent applications by Sungjin Suh, Seoul KR

Patent applications by Sungjun Yoon, Seoul KR

Patent applications by PANTECH CO., LTD.

Patent applications in class Having both time and frequency assignment

Patent applications in all subclasses Having both time and frequency assignment